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Steps>>Translation - Stages of Translation...

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Stages of Translation Prokaryotes » Initiation 1 . 30s subunit [1 – 16s rRNA] + 2 initiation factors [IF1 & 1F3] attached [proteins, NOT ribosomal proteins] 2. 16s rRNA in 30s subunit bond to mRNA’s Shine Dalgarno sequence [SD – AGGAGG - +10] in 5’ untranslated region [upstream from start codon] – association helped by IF3 [easier & quicker] 3. tRNA comes in charged [with amino acid already attached – N-formyl methionine ], put in the right shape to bind in ribosome by IF2 + GTP [control] – complex of tRNA + amino acid [N-fmet] + IF2 + nucleotide GTP] 4. IF1 in A site makes tRNA bind in P site by obscuring A site 5. 50s subunit comes in and binds loosely [IF1, IF2, IF3 are in its way] 6. Lose binding of 50s subunit causes GTP to cleave [split] P + GDP IF2 bound to GDP changes shape IF2 releases all other IFs release GTP controls order of events [1 event triggering another event that triggers [causes] another event] 7. After IFs leave, 50s subunit binds tightly + [30s subunit] 70s ribosome + mRNA , start codon in P site, bound to anticodon of tRNA carrying N-fmet » Elongation – 2 cavaties [P – peptidyl site [polypeptide – chain of amino acids build so far] & A – aminoacyl site [new amino acid brought in by next tRNA]; come/go into ribosome by diffusion; energetically expensive to make proteins 8. new tRNA [complex – tRNA + amino acid + GTP + EF-Tu] wasn’t in right shape unless with complex, floats into A site 9. if aminoacylsnthatase found right tRNA, base pairing [wobble rules] with codon & anticodon – attraction from H bonds pulls down anticodon deforms anticodon deforms tRNA a bit GTP cleaves GDP + P EF-Tu changes shape & dissociates [with EF-Tu in way before, tRNA was bent and could not put amino acid next to polypeptide chain] amino acid can make peptide bond with polypeptide chain --
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